1. Field of the Invention
The present invention relates to an LCD monitor, and more particularly, to a power control system for an LCD monitor.
2. Discussion of the Related Art
In general, a liquid crystal display (LCD) panel included in an LCD monitor displays an image by injecting a liquid crystal into a space between two thin glass plates and varying the voltage of electrodes of the glass plates. The LCD panel does not generate any light by itself. Therefore, it requires a light source in order to enable a user to view an image being displayed on the LCD panel. For the reason set above, a typical LCD monitor includes an LCD panel, a lamp unit providing light to the LCD panel, an LCD inverter and power supply (LIPS) unit supplying the required power to the lamp unit, and a controller controlling the LIPS system. The LIPS unit often employs a control circuit for protecting the lamp unit from being damaged due to a power surge (voltage or current) within the lamp unit.
The control circuit directly senses the voltage (usually higher than 600V) and current being supplied to the lamp unit. When the control circuit detects a voltage surge (or current surge) within the lamp unit, it reduces or cuts off the electric power being supplied to the lamp unit for protecting the lamp unit by sending corresponding control signals. However, the control circuit described above has several problems. First, the control circuit is designed to protect the lamp unit, but not the LIPS system. A voltage surge may occur within the LIPS system that still supplies a normal voltage to the lamp unit. In this case, the control circuit will not be able to detect such voltage surge within the LIPS system. In other words, the control circuit is incapable of preventing the LIPS system from being damaged when any one of the components of the LIPS system does not operate properly. The malfunctioning components and any other unit coupled to such components will be greatly damaged.
Next, if one or more components of the LIPS system do not operate, they may not be properly controlled by the control circuit. Therefore, even when the control circuit detects a power surge of the lamp unit, the LIPS system may not properly reduce or cut off the power to protect the lamp unit as indicated in the control signals, causing the lamp unit to be even more damaged. In addition, the above control circuit directly senses the voltage being supplied to the lamp unit. When an abnormally high voltage (voltage surge) is feedback to the control circuit, the circuit may be damaged. Therefore, a power supply control system that is able to protect the lamp unit as well as a power supply is desired.